This invention is concerned with an improved process for the preparation of 2,6-dialkylaniline which comprises the reaction of 1,3-dialkylbenzene with isobutene in the presence of a hydrogen fluoride catalyst to form 1,3-dialkyl-5-tertiary-butylbenzene, which is subsequently reacted with nitric acid in the presence of a soluble mercuric salt catalyst to form 2-nitro-1,3-dialkyl-5-tertiary-butylbenzene, which is then catalytically hydrogenated to give 2,6-dialkyl-4-tertiary-butylaniline, followed by pyrolysis in the presence of a heterogeneous acidic catalyst.
One method of preparing 2,6-dialkylaniline is by the amination of hydroxy aromatics. U.S. Pat. No. 3,931,298 describes a process for the preparation of aromatic amines by the reaction of hydroxy-substituted aromatic compounds with ammonia in the presence of a catalytic amount of a cyclohexanone and in contact with a hydrogen transfer catalyst.
U.S. Pat. No. 3,960,962 describes a related process wherein aromatic hydroxy compounds are converted to the corresponding aromatic amine by reaction with ammonia in the presence of a cyclohexanone promoter and a catalyst comprising metallic palladium bonded to a phosphinated polystyrene resin.
In U.S. Pat. No. 3,965,182 aromatic amines are made by reacting a phenol with aluminum nitride and either ammonia or a primary or secondary amine.
U.S. Pat. No. 3,801,642 is concerned with a process for replacing an aromatic hydroxyl group with an amine group by forming a metal aryloxide from the corresponding aromatic hydroxy compound and reacting the metal aryloxide with ammonia or a primary or secondary amine in the presence of a Friedel-Crafts catalyst.
U.S. Pat. No. 4,125,560 describes the direct amination of phenols with amines by the ammonolysis of phenols in a liquid phase under pressure with an aqueous ammonia solution containing a catalytic amount of an ammonium salt.
U.S. Pat. No. 3,219,704 describes the preparation of aromatic amines by the condensation of six-membered alicyclic ketones and ammonia compound with a dehydrogenation catalyst, wherein the molar portion of the ketone is at least substantially equal to the ammonia compound.
In U.S. Pat. No. 3,442,950 aminated benzenes are prepared by catalytically reacting a cyclohexanol with an aminating agent. When cyclohexanone is present in the cyclohexanol component, the reaction is initiated in the presence of one mole of hydrogen per mole of cyclohexanone.
The use of isobutene and hydrogen fluoride to alkylate dialkylbenzenes is described in U.S. Pat. No. 2,860,169 to Schlatter.
An article by L. M. Stock and T. L. Wright in the Journal of Organic Chemistry, Vol. 44, No. 20, pp. 3467-3470 (1979), describes the mercuric acetate catalyzed nitration of 1,3-dimethylbenzene. A mixture of isomeric products is obtained, the 4-nitro isomer being the major product. The 2-nitro compound is reported to be obtained in only minor amounts.
Dialkylanilines, and in particular 2,6-dialkylanilines, are useful intermediates for a variety of compounds having herbicidal and fungicidal activity.